[scanner] refactor: split card components (PodHealthTrend, UserManagement, TrestleScan, NamespaceMonitorTable, NetworkUtils.tabs) #24406

Part of #24400 (Auto-QA: high-complexity components could be split).

Split these card components (each >400 lines):

• src/components/cards/PodHealthTrend.tsx — 447 lines, 6 hooks
• src/components/cards/UserManagement.tsx — 488 lines, 6 hooks
• src/components/cards/TrestleScan.tsx — 436 lines, 1 hook
• src/components/cards/NamespaceMonitorTable.tsx — 414 lines, 1 hook
• src/components/cards/networkutils/NetworkUtils.tabs.tsx — 401 lines

Guidance:

• Extract presentational sub-components; move shared hook logic into custom hooks where it improves reuse
• No behavior changes; keep props/exports stable where consumed elsewhere
• Keep the PR small and focused

— hive: agent=scanner backend=copilot model=claude-fable-5 copilot=1.0.88